|Publication number||US5933591 A|
|Application number||US 08/757,518|
|Publication date||Aug 3, 1999|
|Filing date||Nov 27, 1996|
|Priority date||Nov 27, 1996|
|Also published as||WO1998024207A1|
|Publication number||08757518, 757518, US 5933591 A, US 5933591A, US-A-5933591, US5933591 A, US5933591A|
|Original Assignee||Alcatel Usa Sourcing, L.P.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (4), Referenced by (11), Classifications (12), Legal Events (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates in general to local area networks and more particularly to an apparatus for isolating a fault on a local area network.
In order to insure data integrity through a network, systems often employ redundant hardware. If, however, the network itself is a single point of failure, the redundant hardware is useless and failure will occur without an opportunity for recovery. To remedy this situation, systems of interconnected local area networks have been proposed. In these networks, redundant hardware attaches physically to two different local area networks. If one network becomes a single point of failure, operation switches to the second network. This system, however, is expensive since it increases the number of network cards needed to operate the system. Each device would need an additional network card to tie into the redundant LAN. Therefore, it is desirable to provide fault protection in a local area network system without duplicating hardware for redundancy.
From the foregoing, it may be appreciated that a need has arisen for a local area network with fault isolation without unnecessary redundant hardware. In accordance with the present invention, an apparatus for isolating a fault on a local area network is provided which substantially eliminates or reduces disadvantages and problems associated with prior redundant local area network systems.
In accordance with one embodiment of the present invention, an apparatus for isolating a fault on a local area network includes a first local area network and a second local area network. The first local area network and the second local area networks are identical. Also included is a metallic bridge which couples the first local area network with the second local area network, forming a larger local area network. The metallic bridge is operable to decouple the larger local area network into an operable local area network and an inoperable local area network upon a failure in either the first local area network or the second local area network.
The present invention provides various technical advantages over conventional local area network protection devices. For example, one technical advantage is an inexpensive way to provide redundancy in a local area network. Another technical advantage is that failures in both network devices and the local area network media can be isolated quickly without complex equipment. Additionally, once the local area network splits into segments, the devices can determine which of the new segments is viable and continue operation on that segment with minimal interruption. Yet another technical advantage is the ability to continue to pass LAN traffic even during a duration of a failure by allowing protected services to continue to operate. Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions and claims.
For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings, wherein like reference numerals represent like parts, in which:
FIG. 1 provides a block diagram of a local area network system utilizing a metallic bridge;
FIG. 2 provides a detailed layout of the metallic bridge; and
FIG. 3 provides a flow chart of a method of operation.
FIG. 1 provides a block diagram of a network system 10 utilizing a metallic bridge. Network system 10 includes a local area network (LAN A) 12 and a local area network (LAN B) 14 connected by a metallic bridge 16. An operating system (OS) interface 11 connects to LAN A 12 and LAN B 14 and is used to route data from the operating system to the proper elements on these local area networks. In this example, OS interface 11 is not shown to provide protected service due to a circuit failure though such protection may be implemented as desired. A plurality of network processor card pairs 18, 20, and 22 connect to LAN A 12 and LAN B 14. In this example, the services provided by network processor card pairs is protected in case of a circuit or LAN failure. Therefore, each processor card pair is deployed to provide redundant protection for the specially designated access point; for example, a processor card 18a and a processor card 18b of processor card pair 18. Each pair of processor cards, 18a and 18b, can communicate with each other via a connection link 26. Each processor card pair 18, 20, and 22 attaches to metallic bridge 16 via bridge control lines 17. LAN A 12 and LAN B 14 also connect to a number of local elements 13 which are processing entities that can source or sink information between itself and the operating system or processor cards. As shown, local elements 13 are not protected with redundant circuitry though such protection may be implemented as desired.
In operation, metallic bridge 16 connects LAN A 12 and LAN B 14, essentially forming one larger LAN. Pairs of processor cards, such as 18a and 18b, connect to the larger LAN, with processor card 18a attaching to LAN A 12 and processor card 18b attaching to LAN B 14. Since each processor card in a processor card pair are identical, only one operates at any given time. Each processor card in a processor card pair can negotiate between each other via connection link 26 to determine which one is to be in operation. Network processor cards 20 and 22 operate in the same manner.
If a failure occurs, either in a processor card pair 18, 20, and 22 or in LAN A 12 or LAN B 14, metallic bridge 16 opens in response to signals sent over bridge control lines 17, decoupling LAN A 12 from LAN B 14, resulting in two separate segments, one for LAN A 12 and one for LAN B 14. Each pair of processor cards 18a and 18b are now on a separate LAN. The failure is now isolated to either LAN A 12 or LAN B 14 which can be detected by the processor card pairs. Operations continue on the operable LAN through the corresponding processor card.
FIG. 2 provides a detailed drawing of metallic bridge 16. One pair of processor cards, 18a and 18b, is illustrated. Other pairs of processor cards 20 and 22 attach similarly. Processor card 18a connects with LAN A 12 via line 30. Similarly, processor card 18b connects with LAN B 14 via line 32. Switches 40a, 40b, 42a, and 42b are all activated in the closed position, thus connecting LAN A 12 and LAN B 14 together. Switches 40a, 40b, 42a, and 42b are relay switches in the primary embodiment, although it is clear that any of a variety of switching means can be employed. Processor card 18a has a source output 44a and a sink input 46a. Each must be active to keep LAN A 12 and LAN B 14 joined. Processor card 18b also has a source output 44b and a sink input 46b. Again, each must be active to keep LAN A 12 and LAN B 14 joined. Source output 44a attaches to line 48 which in turn connects with switch 40a which in turn connects to sink input 46b which connects to switch 40b which connects back to source output 44a. Similarly, source output 44b connects via line 50 to switch 42b which in turn connects to sink input 46a which connects to switch 42a which connects back to the source output 44b. Finally processor card 18a and processor card 18b connect to monitoring lines 52a and 52b.
In operation, switches 40a, 40b, 42a, and 42b default to the closed position, connecting LAN A 12 and LAN B 14 together and forming one larger LAN. When both processor cards 18a and 18b are functioning normally, their respective source outputs and sink inputs are active. As an example of operation, a signal will source at source output 44a, forcing switch 40a and 40b into the closed position and the signal will then sink at the sink input 46b. If failure in processor card 18a causes a failure to source the signal or if it detects a problem on the LAN and stops sourcing source output 44a, switches 40a and 40b will open. If processor card 18b fails to sink the signal properly or intentionally terminates the signal due to a detected fault, switches 40a and 40b will open. Similarly, source output 44b sources a signal to close switches 42a and 42b. The signal sinks at sink input 46a. Failure in the source or sink of this pair of switches will cause them to open. By using two switches per source and sink and four switches overall, redundancy is achieved. As long as one of the four switches are open, LAN A 12 and LAN B 14 will separate. A power failure would cause all four switches to open.
If there is a failure in the local area network media, LAN A 12 and LAN B 14 can still be separated. For example, if there is a failure in the media of LAN A 12, when processor card 18a attempts to communicate across LAN A 12, its attempt will be unsuccessful. Processor card 18a will then wait a random amount of time and retry transmission. After a certain amount of attempts, processor card will give the signal to open the bridge to separate LAN A 12 and LAN B 14.
During operation, monitoring points on monitoring line 52a and 52b determine the position of the switches. If the switches are all in the closed position, then the monitoring line should be grounded and an impedance to ground will be seen. If a switch moves to the open position, then the monitoring line will be attached to one of LAN A 12 and LAN B 14 and the impedance to ground will cease. The monitoring lines can also determine if all switches open properly in the event of a failure to identify a switch failure.
FIG. 3 is a flowchart of a method for isolating a fault on a local area network. Initially, two identical local area networks, LAN A 12 and LAN B 14, join to form a larger LAN via metallic bridge 16 in step 62. The larger LAN is monitored continuously for failure in step 64. If there is no failure, step 62 repeats. If there is a failure, metallic bridge 16 opens in step 68. Step 70 involves LAN A 12 and LAN B 14 splitting apart, forming an operable LAN and an inoperable LAN. All operations switch to the operable LAN in step 72.
Thus, it is apparent that there has been provided, in accordance with the present invention, an apparatus for isolating a fault on a local area network that satisfies the advantages set forth above. Although the preferred embodiment has been described in detail, it should be understood that various changes, substitutions, and alterations readily ascertainable by one skilled in the art can be made herein without departing from the spirit and scope of the present invention as defined by the following claims.
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|U.S. Classification||714/4.1, 370/220|
|International Classification||H04L29/14, G06F11/20, H04L12/46|
|Cooperative Classification||H04L69/40, G06F11/2007, H04L12/46, G06F11/2005|
|European Classification||G06F11/20C2, H04L29/14, H04L12/46|
|Nov 27, 1996||AS||Assignment|
Owner name: DSC TELECOM L.P., TEXAS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:MAZZURCO, ANTHONY;REEL/FRAME:008347/0971
Effective date: 19961125
|Nov 27, 1998||AS||Assignment|
Owner name: ALCATEL USA SOURCING, L.P., TEXAS
Free format text: CHANGE OF NAME;ASSIGNOR:DSC TELECOM L.P.;REEL/FRAME:009596/0527
Effective date: 19980909
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